US2535217A - Treatment of materials containing tungsten compounds - Google Patents

Description

advantages result:

Patented Dec. 26, 1950 TREATMENT OF MATERIALS CONTAINING TUNGSTEN CONIPOUNDS Kuo Ching Li and Carl Marion Dice, Glen Cove,

N. Y., assignors to Wah Chang Trading Corporation, New York, N. Y., a. corporation of New York No Drawing. Application August 24, 1948, Serial No. 45,982

7 Claims. (Cl. 75-122) This invention relates to the treatment of materials containing tungsten oxide, such as ores, concentrates or the residual products of the beneficiation or treatment of ores or other substances in which tungsten oxides appear. The broad object of the invention is the production of relatively pure tungsten bearing substances, of the class consisting of tungsten carbide or ferrotungsten, from such materials.

More specific objects include the provision of commercial processes by which such tungsten containing products may be produced from complex materials which contain, in addition to tungsten oxide, such elements, or compounds thereof, as tin, copper, arsenic, sulphur, phosphorus, lead, bismuth and antimony.

A further obiect of the invention is a comparativel low cost process of winning relatively pure tungsten products and tin values from oxidic tungsten ores containing substantial amounts of tin values.

The specific objects above indicated have not 'previously been achieved in commercial operation by processes involving the direct reduction of tungsten from tungsten oxide bearing materials. Such processes have always required very high temperatures for operation and whatever metallic values as are present in the tungsten oxide bearing material have been found in the final tungsten bearing product. The present invention provides a method of direct reduction which does not require as high an operating temperature and which prevents foreign metallic values, from entering in any substantial amount into the tungsten carbide or ferrotungsten which is the end product desired. Other advantages of the invention will be noted in, or are apparent from, the following description.

It is the gist of the present invention that the tungsten oxide is reduced and the resulting carbide or ferrotungsten formed in the presence of, or in some cases, during the simultaneous formation of, an alloy of iron and tin. We have found that when this condition is achieved two major first, any metallic values present in the tungsten oxide bearing material, which would otherwise be found in the resulting carbide or ferrotungsten, are preferentially taken up in the iron-tin alloy, and, second, the reduction process proceeds eificiently at lower temperatures. Thus the invention can best be described byinitially considering the product of such a reduction. This product is intermediate in nature and consists, when solidified, of a metallic mixture or alloy essentially composed of a tungsten carbide or ferrotungsten component,

' or both, embedded in a matrix of iron-tin alloy which matrix contains most, if not all, of the other metallic values present as impurities in the tungsten oxide bearing material, the tung- 'sten component of the alloy being substantially free from metallic impurities. Essentially this product is but a source of a final high purity ferrotungsten or tungsten carbide, these materials being separable from the alloy by methods hereinafter described. The amount of iron-tin alloy matrix which appears in the solidified product of the methods of this invention need not be great but should be substantial in the sense that it forms, by weight at least about ten per-cent by weight of the solidified alloy.

The methods of this invention may be performed by establishing a bath of molten irontin alloy and addin to this bath the tungsten oxide hearing are together with carbon suflicient to reduce the same under such conditions of temperature and the like as will insure a satisfactory reduction. However, tungsten ores as they occur in nature carry substantial tin values and some iron values, many tin ores carry some tungsten values and residues resulting from the beneficiation of tungsten ores often carry high tin values and iron values together with residual tungsten values. Since these values may be simultaneously reduced by reaction with carbon the most economical commercial practice of the principles of this invention utilizes as starting materials the cheaper tin and iron values available in such ores and residues. Thus by proper selection and blending of ores, concentrates and residues a charge can be formed in which all of the tin values and iron values necessary to the production of the desired iron-tin alloy are available in inexpensive form and are simultaneously reduced with the tungsten oxide to form the iron-tin alloy with which the resultant tungsten carbide or ferrotungsten also alloys and from which these tungsten bodies crystalize during' solidification. Thus in practice it may be found possible to blend tungsten ores and residues so as to form a charge containing all of the necessary tin values and at least some of the necessary iron values, depending upon whether the product finally desired is ferrotungsten or tungsten carbide and this is the preferred way of forming the ion-tin alloy. Where deficiencies of tin values occur a tin ore may be used to furnish the additional values. Where deficiencies in iron values occur scrap iron or iron ore may be used as a further iron source in the charge.

In any event whether the charge originally contains the necessary iron and tin values or whether the desired iron-tin alloy be preformed and brought separately to the reduction operation it will be found that reduction of the tungsten oxide bearing charge will proceed efiicimtly and satisfactorily at temperatures as low as 2500 degrees Fahrenheit.

The carbon component of the charge may be furnished by any convenient source of carbon such as coal or coke. The amount of carbon in the charge should be at Last sufiicient to reduce the metallic values from their compounds to metallic state. When only sufficient carbon is present to effect this reduction the product of the smelting operation will contain the reduced tungsten values in the form of ferrotungsten. IncrLaSing amounts of carbon in the charge will cause the reduced tungsten values to increasingly appear in the form of tungsten carbide. When the carbon content is such as to provide sufficient carbon to reduce the metallic values of the charge from their compounds to the metallic state and, additionally, enough carban to convert all the tungsten thus reduced to tungsten carbide, the resulting product will contain the tungsten values in the form of carbide usually to the excluson ofa-nyssubstantial amount of ferrotungsten. Thus by control of carbon content of the charge the tungsten values may be recovered as tungsten carbide or as ferrotung- .sten, both forms being useful products in the art particularly when they are relatively pure. The tungsten carbide referred to herein possibly include a small amount of the double iron tungsten carbide (FeiWzC) but, for reasons Which are not apparent, only the monotungsten can bide -(-WC:) is obtained in any quantity by the practice of this invention. The direct winning of the tungsten in the form :of the moniocarbide WC is :a desirable feature of the invention.

was previously noted the desired iron-tin alloy maybe furnished to the reduction operation as such or may be. formed by reductionor smelting \of components of the charge which includes the tungsten oxide values. In any event the amount of tin available should, for best results be :so adjusted that the iron-tin alloy contain between about 15 to 55 percent by weight of tin. Lower amounts down to, Say, percent may be tolerated but will result in unduly raisthe temperatures of operation. High-er amounts of tin appear to have no deleterious effect but are not helpful. With higher amount of tin a tin :rich phase appears which does not seem to add to the :emciency of the operation. The tin iron alloy should in any event contain at-leasta-bout 25 percent by weight of iron. Thus while the invention may be practiced with charges including tin values in amounts less than or more than that required to produce an iron-tin matrix in the solidified smelted product containing between --about Y and 55 percent by weight of tin, the best commercial conditions of operation will be achieved when the smelting charged is adjusted in tin content as aforesaid. Otherwise the exact composition of iron-tin alloy matrix obtained by the smelting process is of little importance. This matrix is essentially an irontin alloy but it contains as above noted all, .or almostall, of themetallic impurities which, otherwise, would appear as deleterious impurities in the ferrotungsten or tungsten carbide phases .of the solidified smelting :product.

The available iron content of the smelting charge may be varied considerably within the .scope of this invention. It is at once apparent.

from the foregoing discussion, that enough icon must be present to satisfy the requirements of the iron-tin matrix alloy if the alloy is not preformed, and in the absence of suflicient carbon "to completely convert the tungsten to tungsten carbide, to form ferrotungsten with the tungsten values. This amount can be determined by simple trial and it has been so determined in the practice of this investigation. It would appear, although this statement cannot be made with finality in an absolute sense, that, in general. iron present :in amount greater than that required to fulfill the intermetallic compound FezW, with tungstcn not converted to carbide, will alloy with the tin to form the matrix iron-tin alloy. At fleastapplication of this general principle, Whether or not it is correct, combined with simple trial, allows ready adjustment of the iron content of the charge to produce the desired result of the methods of this invention. Where the tungsten aoxide materials contain some reducible iron =values these are of course available for the purposes of the process and may be supplemented by other available iron values either in a preformed iron-tin alloy or in the form of reducible iron ore or in the form of scrap iron or in similar form. V

The smelting-charge may be composed, in accordance with the principles above set forth, of various materials. If the tungsten oxide bearing material does not have suflicient tin values the tin values may be added separately, preferably in the form of tin ore, concentrates or other relatively inexpensive sources of tin. The tungsten oxide bearing material will often contain substantial amounts of iron values which may, as is necessary, be supplemented by additions to the charge of reducible iron ore, scrap iron or the like. Calculations of the charge must, of course, treat tin values in terms of available tin values at the temperatures of operation. This can be readily accomplished by observing the fume loss of t n values due to causes such as the sulphur or-chloridecontent of the-charge and the time and temperature of the smelting operation. As much as 35% of the tin charged may be lost as .fume. Such loss however may be readily estimated and suflicient allowance made therefor. Where a carbide free, or substantially carbide .f-ree, tungsten product is desired thesmelting operation must .be conducted in carbon free containers unless allowance be made in calculating the or ginal charge for the presence-of such containers. Carbide free operation can usually be assured under such circumstances by deliberate withholding of sufiicient available carbon to effect complete reduction of the metallic values. Such calculations as these, in order to achieve the principles of operations above outlined, are *within the skill of the art and are only noted here by way of example.

The smelting charge thus formed is placed in any convenient smelting apparatus adapted to the smelting conditions and heated, in the presence of slag forming elements, as above indicated, until reduction is complete. The resultant molten metallic product is separated from the slag and cooled. The cooled intermediate product maybe then, or later, treated to separate the tungsten component or components as such and to recover other metallic values in suitable :form.

In this second, or separation step, various methods may be used. These methods may be usually preceded by crushing the iron-tin matrix i ihflproduct is comparatively brittle.) or otherwise disintegrating or subdividing, the metallic product into discrete particles. At this point it may be advantageous to use known principles of magnetic separation to separate the non-ma netic tungsten component, or components, from the magnetic iron-tin alloy which contains the other metallics reduced during the smelting operation. In addition, or in lieu thereof, chemical methods of separation may be employed. Gravity or flotation separation methods may likewise be used. The comparatively low melting range of the iron-tin matrix also afiords the possibility of re-heating the final product to effect gravity separation of the higher melting point constituents.

While any of these indicated separation methods may be used singly or in combination, the preferred separation procedure, having due regard for the desirability of obtaining a tungsten product of high purity and an effectual recovery of other metallic values, is, in accordance with this invention, essentially a leaching process.

Thus in the preferred practice of the methods of this invention the solidified metallic product of the smelting operation is mechanically reduced, as by crushing or pulverization, to discrete particles. These particles are then leached in an aqueous solution containing chlorine. The chlorine may be furnished as such or as hydrochloric acid or gaseous HCl. Under these conditions the iron values, other than those of the ferrotungsten, and the tin values are converted to their respective soluble chlorides. The tungsten component, ferrotungsten, tungsten carbide or both, remains as insoluble. Also present are insolubles in the form of slimes which will usually contain some tungsten values and also other metallic values as Well as non-metallic values.

Initial separation is made by decantation, filtration or otherwise, of the slimes and insoluble tungsten component from the leaching solution. The tun sten component is then separated from the slimes in any convenient manner, as by washing. The tin values may be precipitated from the leaching liquor and either reused in the 4 smelting charge or otherwise converted by known methods to salable product.

The metallic impurities preferentially taken up in the iron-tin allow matrix may, depending upon the chlorine concentration of the leach liquor and the metal in question, appear as metallics in the slimes or as soluble components in the leach liquor or both. In any case they may, if desired, be recovered in usuable form by known methods.

Some specific examples of preferred operation in accordance with the principles of this invention are as follows:

A. A smelting charge was formed by mixing 100 parts by weight of tungsten oxide bearing material with 10 parts by weight of scrap iron and 10 parts by weight of bituminous coal (ash approximately 12 percent b weight). The tungsten oxide bearing material was a mixture consisting of 66.7 percent by weight of a tungsten ore and 33.3 percent by weight of a residue. The ore and residue assayed as follows:

Per cent Ferrotungsten 86.65 -Slimes 7.89 Leach liquor 0.72 Slag 4.7

B. A charge was formed by mixing 100 parts by weight of tungsten oxide bearing material with 10 parts by weight of iron filings and 20 parts by weight of bituminous coal (about 12% ash). The tungsten oxide bearing material was a mixture consisting of 66.7% by weight of ore and 33% by weight of a residue. The ore and residue assayed as follows:

VVO Sn Fe Cu AS S SiO C Ore 51. 27 3.3 15.45 .29 .23 .70 5.65 Residue 2. 72 23. 84 ll. 70 09 13 60 12. 58 2. 68

The residue likewise contained 0.1 to 0.25% phosphorus. The charge was smelted at about 2750 F. for 2 hours. The resulting metallic alloy was cooled crushed to pass a 14 mesh screen and leached with twice its weight of 20 B. hydrochloric acid until visible reaction ceased. The residual tungsten component (consisting of both ferrotungsten and tungsten carbide) assayed as follows (all figures are percent by weight) W Sn Fe 0 P As Cu 83. 74 0. 4 7. 48 4. 49 0. O2 0. 04 trace contained 85.61 percent of the available tungsten in the charge, the remainder of the tungsten values being found in the leach liquors and slimes.

The carbide thus produced contained only a trace of phosphorus and of copper, about 0.03 percent of arsenic, about 0.03 percent of tin and about 0.01 percent of iron.

We have found it desirable to adjust the slag which, as is well known formed in smelting processes and contains silicious and basic elements of the ores, to insure that the slag present will have a relatively high silicate degree.

Having thus described our invention, we claim:

1. The process of recovering tungsten from tungsten oxide bearing materials which includes reducing said oxide with carbon at temperatures in excess of 2500 Fahrenheit in the presence of iron-tin alloy containing between about 5 to 75 per cent by weight of tin, the total amount of such alloy being such that it mom-poses at least about 10 per cent 'of the total weight of said :aflloy and the tungsten lcontaining product ofzsaid seduction.

l he process of recovering tungsten from tungsten oxide bearing materials which includes rred-ucingsaid oxide with carbon at temperatures in excess of -2500 Farhenhei-t in the presence of iron-tin alloy containing between about to '55 per cent "by weight of tin, the total amount of such alloy being such that it composes at least about 10 per centof the total weightof said alloy and the tungsten containing product of said .recluction.

3. The process of reducing tungsten -oxide rbearing material to obtain tungsten bearing sub- :stances of the class consisting of tungsten carbide and ferrotungsten which includes formin-ga charge containing tungsten oxide, available tin values and iron values and carbon, heating said charge to temperatures in excess of 2500 Fahrenheit, cooling the resultant alloy and separating the tungsten bearing components thereof, the content of said charge beingso adjusted that said tin and iron values are sufficient in amount,

in respect of the tungsten and carbon content of the charge, to form in the resultant alloy at least about 10 per cent by weight of=an iron-tin alloy matrix-containing between about '5 to 75 per cent of tin.

4. The process of reducing tungsten oxide bearing material to obtain tungsten bearing substances .of the class consisting of tungsten carbide and ferrotungsten which includes forming a charge containing tungsten oxide, available tin values and iron values and carbon, heating said charge to temperatures in excess of 2500 Fahrenheit, cooling the resultant alloy and separating the tungsten bearing components thereof, the content of said charge being so adjusted that said tin and iron values are sufiicient in amount, in respect of the tungsten and carbon content of the charge, to form in the resultant alloy at least about 10 per cent by weight of an iron-tin alloy matrix containing between about 15 to 55 per cent of tin.

5. In a process of producing high purity tungsten containing substances of the class consisting of tungsten carbide and ferrotu'ngs'ten and tin values from impure materials containing tungsten oxide and reducible tin compounds, forming a charge of said materials, carbon, and available iron, the amount of tin compound and available iron being so adjusted as to furnish su'fficient tin and iron, in the eventual form of an iron-tin alloy containing 15 to 55 per cent by weight of tin, to compose at least about 10 per cent by weight of the total weight of said iron, said tin and said tungsten containing substance,

8 heating said charge to temperatures over about 2500 Fahrenheit to efiect reduction of reducible compounds therein, separating from the resultant metal alloy so formed said tungsten containing substances and separating the tin values from the remainder.

'6. In a process of producing high purity tungsten carbide from impure materials containing tungsten oxide and reducible tin compounds, forming a charge of said impure materials,available iron and at least sufficient carbon to reduce the metallic compounds of said charge and to convert the tungsten so reduced to WC, the amount of tin compound and available iron in said charge being so adjusted as to furnish suflicient tin and iron, in the eventual form of an iron-tin alloy containing between about 15 to 55 per cent by weight of tin, to compose at least about 10 per cent by weight of the total weight of said tin, iron and tungsten carbide, heating said charge to temperatures in excess of about 2500 Fahrenheit to efiect reduction of the reducible compounds therein, and separating the tungsten carbide from the resultant alloy of "iron, tin and tungsten carbide.

7. In a process of producing high purity ferrotungsten from impure materials containing tungsten oxide and reducible tin compounds, forming a charge of said impure materials, carbon in amount not greater than that required to reduce the reducible compounds of said charge, and available iron, the amount of tin compound and available iron in said charge being so adjusted that the tin content will be sufiicient with a portion of the iron, as an eventual iron-tin alloy containing between about 15 to 55 per cent by weight of tin, to compose at least about 10 per cent by weight of the total weight of said tin, iron and ferrotungsten, and the iron content will be surficient to form said iron-tin alloy and, in addition, to form ferrotungsten with the tungsten, heating said charge to temperatures in excess of about 2500 Fahrenheit to effect reduction of reducible compounds therein, and separating the tungsten carbide from the resultant alloy of iron, tin and ferrotungstcn.

.KUO CHING LI.

CARL MARION DICE.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS

Claims (1)

1. THE PROCESS OF RECOVERING TUNGSTEN FROM TUNGSTEN OXIDE BEARING MATERIALS WHICH INCLUDES REDUCING SAID OXIDE WITH CARBON AT TEMPERATURES IN EXCESS OF 2500* FAHRENHEIT IN THE PRESENCE OF IRON-TIN ALLOY CONTAINING BETWEN ABOUT 5 TO 75 PER CENT BY WEIGHT OF TIN, THE TOTAL AMOUNT OF SUCH ALLOY BEING SUCH THAT IT COMPOSES AT LEAST ABOUT 10 PER CENT OF THE TOTAL WEIGHT OF SAID ALLOY AND THE TUNGSTEN CONTAINING PRODUCT OF SAID REDUCTION.